Sending email from a Shared Mailbox
Users that are permitted access to a shared mailbox (also referred to as a shared email account) are able to send emails from that account as well. This is done by changing the "From" field from your personal email address to the shared email address. However, the "From" field is hidden by default in both the Outlook Desktop App and the Outlook Web App (OWA) so how to do this isn't entirely clear. The directions below provide a guide on how to enable this feature and switch over to send an email from a shared mailbox.
When composing a new message, there is an "Options" tab that appears across the top ribbon of the window. It will appear slightly differently depending on which app you're using to compose an email.
It is in this options tab that you will be able to select to display or hide the "From" field in your messages.
For the Outlook Web App, the option appears as a box to check mark to show the field.
On the Desktop App, you will need to click on the three dots to the far right of the ribbon to show these options. If the field is showing there is a box around the icon.
The top of your new email will now show the "From" field. On the Outlook Web App, the field appears next to the Send button but on the Desktop App it will appear as another line above "To".
To change which mailbox you are sending an email from, click on the little downward arrow at the end of the "From" field. The field will expand and your choices for where to send an email from should be listed. If it is not listed, click on "Other Email Address" on the bottom of the list and enter the email address in the pop-up window that appears.